Aberrant methylation and silencing of IRF8 expression in non-small cell lung cancer

Abstract

The aim of the present study was to investigate the aberrant methylation and altered expression of the interferon regulatory factor 8 (<i>IRF8</i>) gene in non-small cell lung cancer (NSCLC). Pyrosequencing assays were performed on 191 tumor specimens from NSCLC patients. The changes in <i>IRF8</i> mRNA expression, prior to and following treatment with a demethylating agent and methylation itself, were examined in 13 lung cancer cell lines by quantitative polymerase chain reaction (qPCR) and pyrosequencing. IRF8 protein expression was examined in 94 of the 191 NSCLC specimens by immunohistochemical analysis. The <i>IRF8</i> methylation level was significantly higher in the tumor tissues than in matched non-malignant lung tissues (P<0.0001). <i>IRF8</i> was more frequently methylated in tumor tissues compared with matched non-malignant lung tissues, as defined by a predetermined cut-off value (P<0.0001). The <i>IRF8</i> methylation level was strongly correlated with the change in mRNA expression in lung cancer cell lines and with the protein expression level in primary tumors. The <i>IRF8</i> gene was more frequently methylated in patients without an epidermal growth factor receptor (EGFR) mutation than in patients with an EGFR mutation (P=0.015). <i>IRF8</i> methylation correlated with recurrent prognosis in adenocarcinomas (log-rank test, P=0.048). IRF8 protein expression was frequently silenced in males, smokers, patients with non-adenocarcinoma or with wild-type EGFR, or in an advanced stage. <i>IRF8</i> is often silenced by its methylation, which is a frequent event in NSCLC and, therefore, methylation of <i>IRF8</i> may act as a prognostic marker for recurrence. Analysis of <i>IRF8</i> methylation status may provide novel opportunities for improved prognosis and therapy of resected NSCLC.